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Aeolian dunes of central Sweden

Bernhardson, Martin LU (2018) In Lundqua thesis
Abstract
In the Swedish inland there are aeolian deposits present, ranging from scattered single dunes to dune fields of more than 10 km2. These dune fields often pass unnoticed since they presently are covered by vegetation. However, they contain a rich palaeoenvironmental archive. Only a few research papers have been published regarding these aeolian deposits during the last 90 years. The primary scope of this thesis has been to determine why these dunes formed, when they formed, and what they can tell us about the environment during their formation. The results from these investigations are presented in four research papers.

The shape and orientation of a dune is determined by the local environment during its formation, such as the... (More)
In the Swedish inland there are aeolian deposits present, ranging from scattered single dunes to dune fields of more than 10 km2. These dune fields often pass unnoticed since they presently are covered by vegetation. However, they contain a rich palaeoenvironmental archive. Only a few research papers have been published regarding these aeolian deposits during the last 90 years. The primary scope of this thesis has been to determine why these dunes formed, when they formed, and what they can tell us about the environment during their formation. The results from these investigations are presented in four research papers.

The shape and orientation of a dune is determined by the local environment during its formation, such as the abundance of sediment available for entrainment by the wind, groundwater table fluctuations, changes to precipitation and temperature, presence/absence of vegetation, mode of the wind et cetera. By determining the type of dunes it is possible to determine the local environment during their formation. If one also can determine when these dunes formed and stabilised one can determine the palaeoenvironment, and in extension the palaeoclimate, during a specific time period.

In this thesis, new findings are presented regarding the geomorphology, geochronology and palaeoenvironment of a number of dunes and dune fields in south and central Sweden, based on state-of-the-art methods, such as LiDAR (light detection and ranging) based remote sensing and optically stimulated luminescence dating. The previous hypotheses concerning the formation of these dunes have also been evaluated.

The findings show that the dunes of central Sweden are primarily of a transverse type, i.e. their dune ridges are transverse to the dune forming winds and they were formed in a setting devoid of vegetation and with an abundance of sediment. The primary dune forming winds for these transverse dunes appear to have been north-westerly and westerly winds. The investigated dunes further to the south show signs of having been reworked after their initial formation and are often of a parabolic type, i.e. curved/crescentic in shape with their arms facing upwind. These dunes have been described as strongly linked to the presence of vegetation, and can often be considered secondary dune forms. These more southern dunes appear to also mainly have been formed by north-westerly and westerly winds, although they display a bigger scatter in wind directions than the more northern dunes.

The luminescence ages suggest that most of the dunes formed during the early Holocene, and later events of sand drift have been uncommon with only minor impact on the dune morphology. There seems to have been a primary dune stabilisation phase ~10-9 ka, irrespective of the latitude of the dune fields. This means that some dune fields formed close after local deglaciation, while others formed millennia later. This suggests that dune formation and dune stabilisation of central Sweden have been controlled by regional environmental conditions. Extremely low lake levels in southern and south-central Sweden 10.5-9.5 ka BP in conjunction with an unstable climate during early Holocene probably delayed dune stabilisation by vegetation. After the vegetation had stabilised the dunes, they became much more resilient to further fluctuations in the climate. (Less)
Abstract (Swedish)
I Sveriges centrala inland finns det allt från enstaka sanddyner till stora dynfält som täcker mer än 10 km2. Dessa dynfält passerar dock oftast obemärkt i landskapet på grund av det oftast markanta vegetationstäcke som fixerar dessa dyner. De är dock värdefulla för att kunna återskapa forna tiders klimat och vindmönster, men tyvärr har förhållandevis lite forskning angående dessa dyner bedrivits under de senaste 90 åren. De primära frågeställningarna i den här avhandlingen har varit varför dessa sanddyner bildades, när de bildades och vad de kan säga oss om tidigare klimatförändringar. Resultaten från detta arbete presenteras i fyra vetenskapliga artiklar.

Sanddyners form och orientering är beroende av den omgivande miljön under... (More)
I Sveriges centrala inland finns det allt från enstaka sanddyner till stora dynfält som täcker mer än 10 km2. Dessa dynfält passerar dock oftast obemärkt i landskapet på grund av det oftast markanta vegetationstäcke som fixerar dessa dyner. De är dock värdefulla för att kunna återskapa forna tiders klimat och vindmönster, men tyvärr har förhållandevis lite forskning angående dessa dyner bedrivits under de senaste 90 åren. De primära frågeställningarna i den här avhandlingen har varit varför dessa sanddyner bildades, när de bildades och vad de kan säga oss om tidigare klimatförändringar. Resultaten från detta arbete presenteras i fyra vetenskapliga artiklar.

Sanddyners form och orientering är beroende av den omgivande miljön under deras bildning, såsom mängden tillgänglig sand för vindtransport, grundvattennivå, temperatur, nederbörd, närvaro/frånvaro av vegetation, vindmönster m.m. Genom att identifiera en sanddyns form, och således dess typ, är det möjligt att identifiera de ovan nämnda förhållanden vid dynernas bildning. Om man kan bestämma när dessa dyner bildades kan man återskapa miljön, och i förlängningen klimatet, under en specifik tidsperiod.

I den här avhandlingen presenteras resultaten angående ett antal svenska dyner och dynfälts geomorfologi, geokronologi samt deras paleomiljö. Med hjälp av moderna analysmetoder, såsom LiDAR-baserad (light detection and ranging) fjärranalys och luminiscensdatering, har tidigare forskningsresultat utvärderats samt nya resultat presenterats.

Resultaten visar att dynerna i centrala Sverige huvudsakligen är av en transversell typ, d.v.s. deras dynryggar är orienterade i rät vinkel mot de dynbyggande vindarna, och de bildades i en miljö utan vegetation och med god tillgång till sediment. De primära dynbildande vindarna för dessa transversella dyner verkar ha varit nordvästliga och västliga vindar. De undersökta dynerna längre söderut uppvisar tecken på att ha omarbetats efter deras ursprungliga bildning och är ofta av parabeltyp, d.v.s. bågformade med sina armar orienterade motvinds. Denna dyntyp har beskrivits som starkt länkad till närvaro av vegetation, och kan ofta betraktas som sekundära dynformer. Dessa sydligare parabeldyner tycks, liksom de centrala transversella dynerna, huvudsakligen ha bildats av vindar från nordväst och väst. Dock uppvisar de en större spridning i vindriktningar än de nordligare dynerna.

Luminiscensdateringarna av sediment tagna från dessa dyner visar att de flesta av dynerna bildades och stabiliserades under den tidiga delen av Holocen. Senare fall av sanddrift under övriga delar av Holocen var ovanligt, och hade oftast bara smärre påverkan på dynmorfologin. Det verkar ha varit en primär dynstabiliseringsfas ~10-9 ka, oberoende av dynfältens latitud. Detta innebär att vissa dynfält bildades strax efter den lokala deglaciationen, medan andra bildades betydligt senare. Detta antyder att dynbildning och dynstabilisering i centrala Sverige har styrts av regionala klimatförhållanden. Extremt låga vattennivåer i sjöar i södra och syd-centrala Sverige 10,5–9,5 ka BP, i kombination med ett instabilt klimat under tidiga delen av Holocen fördröjde antagligen dynstabiliseringen av vegetationen. Väl täckta av vegetation var dynerna betydligt mer motståndskraftiga mot vinderosion, även under senare klimatförändringar. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Clemmensen, Lars, Department of Geosciences and Natural Resource Management, University of Copenhagen, Denmark
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Aeolian deposits, Inland dune, LiDAR, Digital elevation model, GIS, Luminescence dating, Holocene, Sweden
in
Lundqua thesis
issue
84
pages
117 pages
publisher
Lund University, Faculty of Science, Department of Geology, Quaternary Sciences
defense location
Lecture hall “Pangea”, Geocentrum II, Sölvegatan 12, Lund
defense date
2018-04-06 09:15:00
external identifiers
  • scopus:85055209347
ISSN
0281-3033
ISBN
978-91-87847-38-7
978-91-87847-39-4
project
Aeolian activity in Sweden: an unexplored environmental archive
language
English
LU publication?
yes
id
05f983d6-30a9-40d2-8cfe-b998f766cc37
date added to LUP
2018-03-12 11:04:24
date last changed
2020-01-13 00:32:42
@phdthesis{05f983d6-30a9-40d2-8cfe-b998f766cc37,
  abstract     = {In the Swedish inland there are aeolian deposits present, ranging from scattered single dunes to dune fields of more than 10 km2. These dune fields often pass unnoticed since they presently are covered by vegetation. However, they contain a rich palaeoenvironmental archive. Only a few research papers have been published regarding these aeolian deposits during the last 90 years. The primary scope of this thesis has been to determine why these dunes formed, when they formed, and what they can tell us about the environment during their formation. The results from these investigations are presented in four research papers.<br/><br/>The shape and orientation of a dune is determined by the local environment during its formation, such as the abundance of sediment available for entrainment by the wind, groundwater table fluctuations, changes to precipitation and temperature, presence/absence of vegetation, mode of the wind et cetera. By determining the type of dunes it is possible to determine the local environment during their formation. If one also can determine when these dunes formed and stabilised one can determine the palaeoenvironment, and in extension the palaeoclimate, during a specific time period.<br/><br/>In this thesis, new findings are presented regarding the geomorphology, geochronology and palaeoenvironment of a number of dunes and dune fields in south and central Sweden, based on state-of-the-art methods, such as LiDAR (light detection and ranging) based remote sensing and optically stimulated luminescence dating. The previous hypotheses concerning the formation of these dunes have also been evaluated.<br/><br/>The findings show that the dunes of central Sweden are primarily of a transverse type, i.e. their dune ridges are transverse to the dune forming winds and they were formed in a setting devoid of vegetation and with an abundance of sediment. The primary dune forming winds for these transverse dunes appear to have been north-westerly and westerly winds. The investigated dunes further to the south show signs of having been reworked after their initial formation and are often of a parabolic type, i.e. curved/crescentic in shape with their arms facing upwind. These dunes have been described as strongly linked to the presence of vegetation, and can often be considered secondary dune forms. These more southern dunes appear to also mainly have been formed by north-westerly and westerly winds, although they display a bigger scatter in wind directions than the more northern dunes.<br/><br/>The luminescence ages suggest that most of the dunes formed during the early Holocene, and later events of sand drift have been uncommon with only minor impact on the dune morphology. There seems to have been a primary dune stabilisation phase ~10-9 ka, irrespective of the latitude of the dune fields. This means that some dune fields formed close after local deglaciation, while others formed millennia later. This suggests that dune formation and dune stabilisation of central Sweden have been controlled by regional environmental conditions. Extremely low lake levels in southern and south-central Sweden 10.5-9.5 ka BP in conjunction with an unstable climate during early Holocene probably delayed dune stabilisation by vegetation. After the vegetation had stabilised the dunes, they became much more resilient to further fluctuations in the climate.},
  author       = {Bernhardson, Martin},
  isbn         = {978-91-87847-38-7},
  issn         = {0281-3033},
  language     = {eng},
  number       = {84},
  publisher    = {Lund University, Faculty of Science, Department of Geology, Quaternary Sciences},
  school       = {Lund University},
  series       = {Lundqua thesis},
  title        = {Aeolian dunes of central Sweden},
  url          = {https://lup.lub.lu.se/search/ws/files/46568470/BernhardsonM_PhDthesis_kappa.pdf},
  year         = {2018},
}